1. Field of the Invention
The present invention relates to edgecards and edgecard connectors. More specifically, the present invention relates to edgecards and edgecard connectors with a biasing mechanism to reduce misalignment tolerances between contacts in the edgecard connectors and pads on the edgecards.
2. Description of the Related Art
Edgecards are typically manufactured from printed circuit boards (PCBs) and include surface pads that provide connection to electrical paths called traces on or within the edgecard. The edgecard is inserted into an edgecard connector so that the pads engage with the contacts in the edgecard connector to form a physical and an electrical connection. The distance between adjacent pads, i.e. pad pitch, on the edgecard is typically selected to be the same as the distance between adjacent contacts, i.e., contact pitch, in the edgecard connector.
FIGS. 1 and 2 show an edgecard 200 inserted into a known edgecard connector 100. The edgecard 200 includes a slot 202 for aligning the edgecard 200 with the edgecard connector 100 and includes pads 201 arranged along the edge of the surface of the edgecard 200. For simplicity, the edgecard 200 does not show any traces; however, the edgecard 200 could have surface or interior traces that connect to the pads 201. The edgecard connector 100 includes contacts 101 and alignment pins 102 to align the edgecard connector 100 with a PCB (not shown) when the edgecard connector 100 is connected to the PCB.
Manufacturing tolerances limit how small the pad pitch of an edgecard can be. The tolerances of the pad pitch and the trace routing cannot be controlled within a small enough range, i.e. within tight enough tolerance, for pitches less than 0.8 mm without problems with misalignment between the pads on the edgecard and the contacts of the edgecard connector. This misalignment can result in loss of contact and/or shorting to the adjacent pad. These problems and misalignment are shown with respect to the known edgecard connector 100 in Prior Art FIGS. 1-9.
FIGS. 1 and 2 show the edgecard 200 ideally inserted into the edgecard connector 100 so that the edgecard 200 is centered with respect to the edgecard connector 100 with equal space 103 on each side of the edgecard 200. FIGS. 3-9 show the problems that occur when the edgecard 200 is not ideally centered with respect to the edgecard connector 100.
FIGS. 1 and 2 show the edgecard 200 with ideal float in the slot of the body of the edgecard connector 100 in which the edgecard 200 is center aligned with respect to the edgecard connector 100 so that the spaces 103 on the left and right sides of the edgecard connector 100 are the same. The amount of float is determined by the manufacturing tolerances of the edgecard connector 100 and the edgecard 200. Known float is designed about the center of the edgecard connector 100, and the edgecard 200 can float right or left within the confines of the slot in the edgecard connector 100. This float contributes to the misalignment problems. Because the ideal float of the edgecard connector 100 is center aligned, the pads 201 of the edgecard 200 are also center aligned. The edgecard 200 is ideally centered in FIGS. 1 and 2, allowing for the pad 201 to be centered with the contact 101. Ideally, the edgecard 200 is centered in the edgecard connector 100 throughout the entire mating process.
FIGS. 3-5 shows a type of misalignment in which the edgecard 200 is not centered with the edgecard connector 100 and is aligned with the far left edge of the slot in the edgecard connector 100. That is, the entire float is to right side so that the space 103 in FIGS. 3 and 4 is twice the size of the spaces 103 in FIGS. 1 and 2. As shown in FIG. 5, the pad 201 and the contact 101 are misaligned. Misalignment can result in the contact 101 falling off the edge of the respective pad 201 or even touching an adjacent pad 201.
FIGS. 6-9 show a type of misalignment in which the edgecard 200 is skewed with respect to the edgecard connector 200 so that the edgecard 100 is angularly misaligned with respect to the edgecard connector 100. The float allows the edgecard 100 to become skewed during the mating sequence, and the pad 201 and the contact 101 are also angularly misaligned. In angular misalignment, the beam of the contact 101 can catch the edge of the pad 201, and the pad 201 can dig into the beam of the contact 101, locking the contact 101 into a permanent misalignment or permanently bending the beam of the contact 101.
These misalignment problems can be addressed by manufacturing edgecards and edgecard connectors with tighter tolerances. However, this increases the cost of manufacturing the edgecards and edgecard connectors.